A collapsible lens barrel is used in an image-taking apparatus such as a digital still camera. The collapsible lens barrel changes its length in an image-taking state in which the distance between a plurality of lens units changes to perform zooming and focusing, and in a housed (collapsed) state in which the distance between the plurality of lens units and the distance from between the plurality of lens units to an image-pickup plane reduce to a predetermined distance. Such a collapsible lens barrel is driven by a driving mechanism such as a cam and a helicoid gear.
Miniaturization of the lens barrel is required with miniaturization of the image-taking apparatus, and quiet drive of the lens barrel is required for reduction of the volume and weight of the lens barrel. For this purpose, in Japanese Patent Laid-Open Application No. H05-150152, a lens driving mechanism is disclosed, in which a lens unit is driven in the optical axis direction thereof by a voicecoil motor including a magnet arranged around the lens unit, and a coil and yoke arranged around the magnet.
However, since a voicecoil motor does not have a stable stop position (for example, a magnetic stable position in a stepping motor) in a nonenergized state, the position of the lens unit driven by the voicecoil motor in the optical axis direction is not held in the nonenergized state such as a nonuse state of the image-taking apparatus. Therefore, there is a problem that the lens unit moves in its movable range in the nonuse state.
When the lens unit having no stable stop position collides a mechanical end of the movable range, deterioration of the optical accuracy of the lens barrel and a collision sound will occur.